The present invention relates generally to an ink cartridge that supplies ink to a recording head, and, in particular, to an improvement in the protection of the ink bag of an ink cartridge wherein the ink bag is accommodated in a case main body along with an ink depletion detecting plate affixed to the ink bag.
Generally an ink jet recording apparatus is designed to print data by causing the recording head thereof to reciprocally move along the width of a recording sheet. Ink is supplied from an ink supply source to the recording head. As a result of such a construction, an ink jet recording apparatus that must produce a large number of copies must carry a large-sized ink cartridge, which cannot be mounted on a carriage. Hence, the ink cartridge is mounted on the housing of the recording apparatus and the ink is supplied to the recording head through a tube.
Reference is made to FIG. 16 in which an example of such a prior art ink jet recording apparatus is shown. A case main body 63 contains an ink bag 62 which includes an ink supply port 64. Ink cartridge 61 is connected via a tube 65 to a sub tank 66 located on a carriage 67. In this manner, ink can be supplied from the sub tank 66 to a recording head affixed to a lower surface of the carriage 67. The apparatus housing 60 also contains a waste ink tank 70.
Supplying the ink in this manner significantly increases the number of copies that can be printed by using only one cartridge as compared with the case where the ink cartridge is mounted on the carriage. However, the large size of the ink cartridge results in a large recording apparatus, which is a problem.
Unexamined Japanese Patent Publication No. Hei. 5-16378 discloses the design of such an ink cartridge. An ink depletion detecting plate 69 (FIG. 17) is secured to the upper surface of the flexible ink bag 62 to cover part of the upper surface of the ink bag. The ink depletion detecting plate has a detecting piece which projects out from a side thereof and aligns with a window located in the case main body. A displacement of this detecting piece is sensed by an ink end detector disposed on the main body of the recording apparatus.
In an effort to overcome this problem, the ink bag 62 has been accommodated in a housing 60 in such a manner that a side surface along the length of the ink bag 62 extends vertically with respect to the corresponding side surface of the housing 60, thereby decreasing the area needed to mount the ink cartridge 61 which results in the desired downsizing of the recording apparatus. Additionally, the size of the ink bag is increased to use any dead space within the housing which results in an increase in the ink capacity of the recording apparatus.
The prior art ink bag has been satisfactory. However, an increase in the size of the ink bag results in an increase in the area that is not covered by the ink depletion detecting plate. Subsequently, when the ink bag is subjected to vibrations during transportation or if the ink cartridge is dropped, the area of the ink bag 62 not covered by the ink depletion detecting plate 69 is shaken at a large amplitude. This results in the collision of the uncovered area of the ink bag with the side walls of the case main body. The uncovered area of the ink bag can also be subjected to bending, twisting or rubbing of the ink bag boundary with the ink depletion detecting plate. Consequent damage to the ink bag can result in the breaking of the bag or impairment of its air shielding characteristics.
Further, to prevent deformation of the ink bag and thereby ensure stable, consistent discharge of ink to the recording head, the shape of the ink bag is maintained by securing a flat area of the ink bag to the bottom on the case main body 63. Additionally, this attachment prevents damage to the ink bag 62 during transportation.
However, in some cases, shaking of the ink at the time when the bottom, flat surface of the ink bag is affixed to the case main body with an adhesive 68, results in the creation of wrinkles on the thus attached surface of the ink bag. These wrinkles extend parallel with the short side of the rectangular ink bag. Moreover, ink bags prepared by using a thick film to increase air shielding characteristics have wrinkles that do not collapse. These wrinkles cause problems with the flow of the ink resulting in the blockage of the ink to the ink supply port 64 which in turn causes the ink to stagnate in the ink bag. Additionally, the wrinkles cause the ink depletion detecting plate to float by a certain height G from the bottom of the ink cartridge. This condition persists even when there is no more ink left in the ink bag thus preventing the accurate detection of an ink end.